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In Amsterdam, Dijkboom b.v. can regularly be found near the famous canal houses. Or rather: under the famous canal houses, because the company has specialized in soil remediation, demolition and groundwork in connection with foundation repair and the construction of cellars. This can be quite a challenge especially in the capital city with its swampy peat soil, centuries-old wooden foundations and monumental buildings. But thanks to the use of Bobcat excavators, the work has become a lot easier, according to a visit to a Dijkboom project.
Working on foundations or building basements under canal houses in Amsterdam is not easy due to the narrow streets, heavy traffic and limited space. To get under the houses, a 1-by-2-meter hole must first be dug in the garden, sidewalk or even in the public road alongside the house. Then a passage in the existing wall of the exterior foundation or facade is broken or cut. The hole and the passage under the house are propped up with sheet pile walls and steel beams so there is no danger of subsidence or collapse. Dijkboom then lowers a small Bobcat excavator into the hole, which begins digging away the soil under the house. Once there is enough room, the mini-excavator can drive under the house, dig and transport the soil to the hole. There it is scooped into containers by a larger excavator, which disposes of the soil - 15 to 25 cubic meters per day, depending on the type of soil and maneuvering space.
To shovel away soil from the hole next to the house in Amsterdam, Dijkboom is using a new E55 from Bobcat, which was recently delivered. The boom of the E55 has an extendable section, which allows the boom to be extended by 60 centimeters. This allows the machine to dig deeper, as well as reach under the house directly from the street. Conveyors or E10 excavators from Bobcat are used to transport the soil under the house, depending on the subsoil. Especially in case of swampy ground with thin mud, the E10 mini-excavator is preferred. Dijkboom has five of them, both diesel versions and an electric machine. The electric E10e is mainly used when the space below is difficult to ventilate. Dijkboom uses various attachments such as a demolition hammer, grapples and various buckets. The company has had a special stainless steel bucket designed to which mud or silt does not stick, which greatly improves productivity.
A basement is being built under the mansion in Amsterdam. The floor area of the building is about 12 by 12 meters. Under part of the house there was already a small basement of 6 by 6 meters of space; under the rest of the floor there was only a crawl space of about 60 centimeters high. The soil under the house will be excavated to a depth of about 3 meters. The groundwater is very high, which means that despite the use of a water pump, a thick layer of silt is constantly being created, in which the machines have to work. When the desired depth is reached, drainage is laid on the soil, a layer of sand of about 10 centimeters is applied, on which a 30-centimeter thick reinforced concrete floor is poured. Ultimately, the new basement will have a headroom of about 2.40 meters. If necessary, demolition work and improvements or special modifications to the existing foundation are also made, after which a contractor completes the basement.
Like most old, Amsterdam buildings, there are wooden piles under the mansion in question on which people used to brick a foundation after applying undergrowth. These piles have a diameter of about 30 centimeters and a length of up to sometimes 14 meters to reach a solid sand layer.
In preparation for the projects, of course, thorough soil and foundation investigations are conducted to assess whether basement construction is possible. Outdoor measurements are also taken on facades before and during construction to verify that the building is not subsiding as a result of the work. In certain areas of the city, archaeological investigations are also sometimes carried out during the work.
According to Johan Eikelenboom, co-owner of Dijkboom, the job in Amsterdam is a good reflection of the kind of projects, which Dijkboom performs mainly in the cities of Rotterdam and Amsterdam. “In those cities there are a lot of problems with old foundations, but in this project the foundation is in reasonable condition,” he says. “And here there is also relatively a lot of space because the house has a small front yard and is next to a parking lot. There was enough space at the house for the hole and the E55, and along the road several containers for soil disposal, a compressor and a construction shack could be placed. In narrow streets, we have to make the hole inside the floor resulting in the residents having to leave their premises during the work.”
In Dijkboom's projects, it often starts with foundation repair, but because people want more living space, building a basement is interesting. That means quite an investment, but there are many possibilities, according to Eikelenboom. “We have worked on projects where swimming pools, garages and a movie theater have been constructed under houses.”
Dijkboom is a sister company of Anton van Dijk Sloopwerken, a company that itself also has about 20 Bobcats in use. They were all supplied by Inter-Techno, which incidentally serves many customers in the demolition sector because the small Bobcat mini-excavators and skid steer loaders are excellent for use indoors and in tight spaces. Klaas van der Vis, operator on the project in Amsterdam, is especially clear: “Bobcat mini-excavators are perfect for our work. They are small, low and quiet, and run a whole working day without any problems.”
